Compressor cooling system using heat exchanger pre-condenser, and compressor provided from a cooling system

ABSTRACT

The present invention pertaining to the field of refrigeration equipments was designed to allow an unexpected construction and operation, and which is more efficient than the one achieved by using existing similar equipments. It is consisted of a compressor ( 1 ) comprised of a shell ( 2 ) within which it is located a compression cylinder ( 3 ), whereas from the shell ( 2 ) it is projected an inlet tube ( 5 ) from an evaporator and a discharge tube ( 6 ), which conducts the fluid into a condenser; at least one pre-condenser ( 7 ) associated with the compressor ( 1 ), the pre-condenser ( 7 ) being fed by a tubing ( 8 ) from the compression cylinder ( 3 ) located within the compressor ( 1 ), and equipped with an outlet tube ( 11 ); and a heat exchanger ( 91 ) internal to the outer region of the compressor ( 1 ) and cooperative with the pre-condenser ( 7 ) through the outlet tube ( 11 ) of the pre-condenser ( 7 ), the heat exchanger ( 91 ) comprising tubes attached around the shell ( 2 ) of the compressor ( 1 ).

FIELD OF THE INVENTION

The present invention relates to a compressor cooling system—morespecifically micro compressors—by using a pre-condenser, which pertainsto the field of refrigeration equipments and that was designed to enablea more efficient operation that the one achieved by using the knownsystems.

BACKGROUND OF THE INVENTION

As it is known in the art, the refrigeration cycle typically consists ofa compressor that transforms the low pressure gas into high pressure andhigh temperature gas that goes into a condenser, where such gas becomesa high pressure subcooled liquid that, then, goes into an expansiondevice that reduces the fluid pressure in order to conduct it to theevaporator that will transform the subcooled liquid into lowpressure—saturated vapor, to further be conducted through the suctionline to enter again into the compressor and start a new refrigerationcycle.

Due to their operation characteristics, compressors usually constitutethe hottest part of a refrigeration system, the temperature thereofbeing a function of room temperature where the system is located.However, the inner temperature of compressors have limits that may beextrapolated in case of the room temperature being too high; besides,the operation temperature of the compressor also influences bearingdesign that will be used therewith—and which should be submitted toharsh approval tests in order to endure the operation under suchconditions. Furthermore, a large part of the compressor inefficiency isassociated with the consequent coolant gas overheating during its pathbetween the suction valve and the compression cylinder, as well as withthe coolant heating during its compression.

The heating of the coolant through the suction path is caused by heatexchanges with the compressor components, which are hotter than thecoolant fluid. In turn, the coolant heating in the compression processmainly occurs due to the addition of work imposed by piston and also,due to a heat part from the cylinder walls at the early stages ofcompression.

Regarding the heating during compression, from the instant that thecoolant temperature exceeds the temperature of the cylinder walls, suchheating could be avoided if the heat exchange between the wall and thecylinder were intensified. However, as the compression is too fast andthe heat exchange area is small, the heat exchange is insufficient inavoiding heating, resulting in high coolant temperature values at theend of the compression. In addition, the temperature of the cylinderwalls is high, which prolongers the coolant heating time over thecompression cycle.

As a consequence of the coolant heating during compression, the heatedcoolant becomes the greatest heat source of the compressor, being themain responsible for heating the compressor components and, therefore,the coolant heating along the suction path. Therefore, effectivesolutions that allow cooling the coolant during its compression processor that reduce the gas temperature after compression (heat sourcereduction), will have an impact on the compression efficiency and,consequently, will impact on losses due to the overheating of thecoolant during the suction.

Some technological solutions were developed to achieve this goal; amongthem there is the one disclosed in document EP0173013, which providesthe use of an outer heat exchanger located in the system suction line inorder to reduce gas temperature before entering the compressor without,however, provide any form of attenuating the gas heating that occursduring the compression step.

On the other hand, document U.S. Pat. No. 4,936,112 describes acompressor equipped with only an inner heat exchanger comprising aplurality of resistive plates welded to each other (or possibly a coil)exclusively directing reducing the temperature of the compressor motor.

Document JP5209596 describes a rotatory-type compressor having anelement named “precooler” to cool the compressed gas that exits thecompressor and to redirect it back to the inside thereof even throughdirecting reducing the compressor inner temperature through said gashaving the temperature attenuated—which presents limitations inefficiency, due to the high temperature reached by the equipment duringoperation. Similarly, document U.S. Pat. No. 5,439,358 describes the useof gas recirculation ducts associated with a manifold having a pluralityof heat exchangers that, however, do not effectively attenuate thetemperature of the air compressor from which part the air to such ducts.

It is noted, therefore, that the solutions employed in the present stateof the art direct the reduction of gas temperature without, however,providing means for additional and simultaneous cooling of thecompressor equipment itself in a more direct and effective manner.

OBJECTIVES OF THE INVENTION

In view of those drawbacks and for the purposes of solving them, is oneof the objectives of the present invention to provide a cooling systemthat directs removing heat from the compressor surface, so as to reducethe gas temperature during the compression process.

Another objective of the invention is to provide a cooling system ableto decrease the gas overheating in the suction path simultaneously tothe cooling of compressor itself, through the use of an outer heatexchanger that plays the role of rejecting heat from the compressedfluid to the external environment, functioning as a pre-condenser.

The presented system further provides the existence of an outer heatexchanger, wrapped on the compressor, which is very effective due toevaporative process of two-phase fluid and to the mechanism of heatexchange by conduction in the component to be cooled. Therefrom, it isestablished the surface temperature of the compressor (and therefore ofthe internal components thereof) close to the pre-condenser saturationtemperature, enabling the compressor operation for high roomtemperatures.

It is further another object of the present invention to disclose acompressor cooling system that can decrease productivity losses byoverheating in the suction, besides improving the compressor energyefficiency.

SUMMARY OF THE INVENTION

The present invention achieves the abovementioned objectives through acompressor cooling system by using a pre-condenser which, according tothe preferred embodiment of the present invention, comprises: acompressor comprised of a shell within which it is located a compressioncylinder, whereas from the shell it is projected an inlet tube from anevaporator and a discharge tube which conducts the fluid into acondenser; at least one pre-condenser associated with the compressor,the pre-condenser being fed by a tubing from the compression cylinderlocated within the compressor, and equipped with an outlet tube; and aheat exchanger internal to the outer region of the compressor andcooperative with the pre-condenser through the outlet tube of thepre-condenser.

According to a preferred embodiment of the present invention, said outerheat exchanger comprises tubes fastened around the compressor or microcompressor shell.

Optionally, the presented system can operate in series, together with anadditional inner heat exchanger located in the compressor andcooperative with the pre-condenser through a spring-tube connected tothe end of the outlet tube of the pre-condenser, such an inner heatexchanger being located within the shell and positioned close to hotpart of the compressor—preferably close to the compression cylinder orcompression cylinder cap, when applicable—, said inner heat exchangerreceiving the fluid from the pre-condenser or from the outer heatexchanger through a spring-tube connected to the end of outlet tube ofthe pre-condenser, and conducts the fluid therein processed into thedischarge tube through an output spring-tube.

The present invention further comprises a compressor equipped with acooling system that contains: a compressor or micro compressor comprisedof a shell within which it is located a compression cylinder, whereasfrom the shell it is projected an inlet tube from an evaporator and adischarge tube which conducts the fluid into a condenser; at least onepre-condenser associated with the compressor, the pre-condenser beingfed by a tubing from the compression cylinder located within thecompressor, and equipped with an outlet tube; and a heat exchangerinternal to the outer region of the compressor and cooperative with thepre-condenser through the outlet tube of the pre-condenser.

In a possible embodiment of the present invention, such compressorequipped with a cooling system can further include at least one innerheat exchanger located in compressor and cooperative with thepre-condenser through a spring-tube connected to the end of outlet tubeof the pre-condenser.

Said objectives are achieved, therefore, by a compressor cooling systemcomprising means for reducing the temperatures of the heat sources ofthe compressor equipment, and, thus, reducing the compression initialtemperature and improving the efficiency in compression.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures show:

FIG. 1—shows a schematic perspective view of a figure by showing acompressor that is cooperative with a pre-condenser and an outer heatexchanger built according a preferred embodiment of the presentinvention.

FIG. 2—shows a diagram schematically illustrating a refrigeration systembuilt in accordance with the preferred embodiment of the presentinvention illustrated in FIG. 1.

FIG. 6—shows in schematic perspective the embodiment described in thediagram in FIG. 5.

FIG. 3—shows an elevated view of the heat exchanger that is associatedwith a compressor built according to the preferred embodiment of thepresent invention.

FIG. 4—shows a plan view of the equipment illustrated in FIG. 3.

FIG. 5—shows an elevated view having a partial longitudinal cut of analternative embodiment of the compressor provided from the refrigerationsystem, which is additionally equipped with an inner heat exchangercoupled to the compressor cylinder cap.

FIG. 6 shows a partial transverse cross-sectional and schematic view ofFIG. 5 showing a second possible embodiment for the invention, in whichthe inner heat exchanger is coupled to the compressor cylinder.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be described hereinbelow in more details based on theimplementation examples represented in the accompanying drawings.

As illustrated in FIG. 1, the compressor cooling system using a heatexchanger and a pre-condenser that is the object of this invention iscomprised of: a compressor 1 associated with a pre-condenser 7, and aheat exchanger 91 located in the shell 2 of the compressor 1 andcooperative with the pre-condenser 7.

FIG. 5 evinces in details that the compressor 1 is comprised of a shell2 within which is it localized a compression cylinder 3 and therespective cap thereof 4—except for the case of using micro compressors,which do not present inner cap—from the shell 2 being projected an inlettube 5 from an evaporator (not shown), and an outlet tube 6 thatconducts the already compressed and processed fluid into a condenser(not shown), the compressor 1 being further equipped with a tubing (ortubes) 8 and 1 of interconnection with the pre-condenser 7 wherewith itcooperates, the pre-condenser 7 being fed by a pipe 8 from thecompression cylinder 3 located within the compressor 1,—as it may bebetter noticed from FIGS. 5 and 6.

According to the preferred embodiment of the present inventionillustrated in FIGS. 1 and 2, the heat exchanger 91 consists of pipesarranged around the compressor or micro compressor 1 shell, coating ittotally or partially.

According to such a construction, as the pre-condenser 7 works at thesame condenser temperature as the refrigeration system does, it isassured that compressor 1 coated by the heat exchanger 91 will have alow temperature which is close to the condensation temperature, due tothe evaporative heat exchange occurring in pipes 91 arranged around thecompressor 1.

It is worth to notice that both the compressor cooling system and thecompressor itself equipped with a cooling system may comprise anadditional heat exchanger 9 positioned within the compressor 1,operating in series with the heat exchanger 91 and with thepre-condenser 7.

Such additional inner heat exchanger 9 preferably should be positionedwithin the shall 2 close to a hot part of the compressor 1, the innerheat exchanger 1 receiving the fluid from a pre-condenser 7 through aspring-tube 10 connected to the end of the outlet tube 11 of thepre-condenser 7, and conducts the fluid therein processed into thedischarge tube 6 through an output spring-tube 12.

FIG. 5 illustrates a first constructive possibility for said additionalinner heat exchanger 9, whereby the same operates coupled to acompression cylinder 3 of the compressor 1.

Another embodiment of the present invention is presented in FIG. 6, inwhich the additional inner heat exchanger 9 is coupled to the cap 4 ofthe compression cylinder 3, when available (noticing that microcompressors do not present an inner cap).

The system of the present invention utilizes the gas itself that iscompressed and pumped by the compressor 1 in order to transport heatfrom inside the compressor 1 into the external environment. Generally,the gas used follows its path in the compressor 1 through the cap 4 ofthe compression cylinder 3, discharge filters, discharge pipe andfinally the discharge tube 6 into the condenser (not shown).

When exiting the compressor 1, the compressed gas rejects heat to theexternal environment through the pre-condenser 7, in which the coolantis brought to the saturation zone. The coolant temperature—which now canbe considered diphase—at the end of the pre-condenser 7 is the owncondensation temperature of the refrigeration system. The coolant, whenexiting the heat exchanger 7 with a lower energy degree (enthalpy),returns to the compressor 1 and is conducted through the pipes 91 alongall outer surface of the shell 2 of the compressor 1. The diphasecoolant then exchanges sensitive and latent heat with the heated body ofthe compressor, reducing the temperature thereof. After accomplishingthe heat exchange, this fluid is directed to the discharge tube 6 whichthen configures the interface of compressor 1 with the other componentsof the refrigeration system.

It is worth to stress that the heat exchanger 91 has the function ofremoving heat from hot parts of the compressor 1 and, consequently,reducing losses by overheating the gas in the suction path andcompression. The use thereof also directs interconnecting the shelltemperature of compressor 1 with the condensation temperature, thenpreventing the compressor 1 from collapsing when working at high roomtemperature.

Furthermore, the pre-condenser 7 allows maintaining the surfacetemperature of the compressor very close to the system condensationtemperature, something that is hard to achieve just by means ofventilation.

In cases where the presented system utilizes an additional inner heatexchanger 9, examples of components that can be cooled include thecompression cylinder 3 and cap 4 of the compression cylinder 3.

When the component to be cooled is the compression cylinder 3, asillustrated in FIG. 6, the compressed fluid exits the compressor 1through the tubing 8, rejects heat in the pre-condenser or outer heatexchanger 7, and returns to the compressor 1 through the outlet tube 11of the pre-condenser 7. When reentering the compressor 1, the cooledfluid is conducted through a spring-tube 10 into the inner heatexchanger 9 coupled to the compression cylinder 3. When exiting theinner heat exchanger 9, the fluid is sent through another spring-tube 12into the discharge tube 6—which is the interface in which the compressedfluid is delivered to the condenser or the refrigeration system.

The heat exchanged in the compression cylinder 3 reduces the walltemperature of the cylinder 3 and further the fluid temperature in thesuction chamber S; therefore, besides the coolant fluid entering colderthe cylinder 3, the heating therein is reduced and the heat exchange tothe walls during compression is maximized, providing the compressionprocess with a greater thermodynamic efficiency.

Alternatively, as illustrated in FIG. 5, the inner heat exchanger 9 canbe coupled to the cap 4 (when available) of the compression cylinder 3.In this configuration, the compressed fluid exits the compressor 1through the feed tubing (pipe) 8 of the pre-condenser 7, rejects heat inthe pre-condenser 7, and returns to the compressor 1 through the tube11. When reentering the compressor 1, the cooled fluid is conductedthrough a spring-tube 10 into the inner heat exchanger 9 coupled to thecap 4 of the compression cylinder 3. Analogously to what happens in thepreviously provided embodiment, when exiting the inner heat exchanger 9,the fluid is directed through another spring-tube 12 into the dischargetube 6 that conducts the compressed fluid into the condenser of therefrigeration system.

The heat exchanged in the cap 4 of the cylinder 3 reduces thetemperature of the compressed gas inside and in all parts of the head.Because the compressed gas is the main heat source of compressor 1,reducing the temperature thereof causes overall temperature reduction ofthe compressor 1 components. Thus, there is a reduction in the initialcompression temperature, which results in a greater thermodynamicefficiency in the compression process.

The benefits of using compressor cooling system using the pre-condenser7 that is the object of this invention are related to reliability andenergy efficiency aspects. Regarding the reliability, the cooling of thehot parts of compressor 1 caused by the proposed system avoids criticaltemperatures in which the existing oil in compressor 1 could suffer fromdegradation and irreversible changes in the thermal-physical propertiesthereof.

However, the greatest benefits are associated with the increased energyefficiency of compressor 1. By transporting heat from hot parts ofcompressor 1 into the external environment, there is a decrease of gasoverheating in the suction path, resulting in an increased density ofthe coolant at the beginning of the compression process and, thus,increasing the amount of mess compressed and pumped by compressor 1.Consequently, there is an increase in the performance coefficient (COP)of compressor 1.

The proposed solution also generates benefits for the operation of therefrigeration system as a whole. By adding a pre-condenser 7, there is agreater heat exchange into the external environment, resulting in lowertemperature of the coolant which circulates through the discharge tube6. Thus, with the coolant being delivered to the cooling system at alower temperature, the condenser is oversized, resulting in thereduction of condensation system pressure.

Therefore, it is increased the efficiency of the refrigeration cycle,because it reduces the required temperature difference for the heatexchange. In addition, as the condenser becomes oversized, there is alsoa decrease in the pull down peak pressure, which is a situation that ismost critical for compressor 1, in which the possibility of occurringtumbling due charge and temperature excess in the same.

It is worth to say that although a preferable constructive way of thepresent invention have been shown, it is understood that any omissions,substitutions and constructive changes can be accomplished by a personskilled in the art, without departing from the spirit and scope of theclaimed protection. It is also expressly provided that all combinationsof the elements that perform the same function in the substantially sameway to achieve the same results are within the scope of the invention.Replacing elements of an embodiment described by other ones are alsofully intended and contemplated

However, it should be understood that the description provided based onthe figures above relates only to some of the embodiments that arepossible for the system of the present invention, the real scope of theobject of the invention being defined in the appended claims.

1. A compressor cooling system CHARACTERIZED in that it comprises: acompressor (1) comprised of a shell (2) within which it is located acompression cylinder (3), whereas from the shell (2) it is projected aninlet tube (5) from an evaporator and a discharge tube (6) whichconducts the fluid into a condenser; at least one pre-condenser (7)associated with the compressor (1), the pre-condenser (7) being fed by atubing (8) from the compression cylinder (3) located within thecompressor (1), and equipped with an outlet tube (11); and a heatexchanger (91) internal to the outer region of the compressor (1) andcooperative with the pre-condenser (7) through the outlet tube (11) ofthe pre-condenser (7).
 2. A cooling system according to claim 1,CHARACTERIZED in that the heat exchanger (91) comprises tubes attachedaround the shell (2) of the compressor (1).
 3. A cooling systemaccording to claim 1, CHARACTERIZED in that the pre-condenser (7) andthe heat exchanger (91) cooperate with at least one additional innerheat exchanger (9) located in the compressor (1), the inner heatexchanger (9) cooperating with the pre-condenser (7) through aspring-tube (10) attached to the end of the outlet tube (11) of thepre-condenser (7).
 4. A cooling system according to claim 3,CHARACTERIZED in that the additional inner heat exchanger (9) is locatedwithin the shell (2) and it is positioned together with a hot part ofthe compressor (1), the additional inner heat exchanger (9) receivingthe fluid from the pre-condenser (7) through a spring-tube (10) attachedto the end of the outlet tube (11) of the pre-condenser (7), andconduces the fluid therein processed into the discharge tube (6) throughan outlet spring-tube (12).
 5. A cooling system according to claims 3and 4, CHARACTERIZED in that the additional inner heat exchanger (9) iscoupled to the compression cylinder (3).
 6. A cooling system accordingto claims 3, 4 and 5, CHARACTERIZED in that the additional inner heatexchanger (9) is coupled to the cap (4), when available, of thecompression cylinder (3).
 7. A compressor provided from a cooling systemCHARACTERIZED in that it comprises: a compressor or micro compressor (1)comprised of a shell (2) within which it is located a compressioncylinder (3), whereas from the shell (2) it is projected an inlet tube(5) from an evaporator and a discharge tube (6) which conducts the fluidinto a condenser; at least one pre-condenser (7) associated with thecompressor (1), the pre-condenser (7) being fed by a tubing (8) from thecompression cylinder (3) located within the compressor (1), and equippedwith an outlet tube (11); and a heat exchanger (91) internal to theouter region of the compressor (1) and cooperative with thepre-condenser (7) through the outlet tube (11) of the pre-condenser (7).8. A compressor according to claim 1, CHARACTERIZED in that it comprisesat least one additional inner heat exchanger (9) located in thecompressor (1), and which cooperates with the pre-condenser (7) througha spring-tube (10) attached to the end of the outlet tube (11) of thepre-condenser (7).